1. Field of the Invention
The present invention relates to semiconductor manufacturing, and, in particular, to a technique for implementing a ball grid array (BGA) fabrication line.
2. Description of the Related Art
Due to the popularity of surface mount technology, the demand for semiconductor devices in ball grid array (BGA) packages is increasing. However, the ball mounting process (e.g., mounting solder balls to the bottom of a BGA package which are reflowed to form contacts with solder pads on a board or flex circuit) is very expensive. As shown in FIG. 1, a conventional BGA ball mount line 100 comprises a ball mount cell 104, a reflow oven 108, and a flux cleaner 110. Ball mount line 100 further comprises a loading cell 102 at its beginning, an offloading cell 112 at its end, and transfer cells 106 between ball mount cell 104 and reflow oven 108 and between flux cleaner 110 and offloading cell 112. Ball mount cell 104 typically comprises a fluxer 114 that applies flux to a BGA package, a sphere mounter 116 that applies solder balls (spheres) to the BGA package under heat and pressure, and a post mount inspection station 118 that inspects the solder balls for proper mounting. Typical ball mount cells, such as ball mount cell 104, are configured to be operated from only one side of the BGA ball mount line (e.g., with an operator positioned at location 120 in FIG. 1).
A conventional BGA ball mount line is long (e.g., about 11.5 meters), requiring substantial floor space, consuming substantial quantities of power and water, and requiring a significant capital investment. Additionally, a conventional BGA ball mount line requires a dedicated operator to operate the ball mount cell.
The present invention provides a method for mounting solder balls on a ball grid array which improves the utilization of labor, water, and electrical power while reducing capital investment. According to the present invention, a BGA ball mount line is configured with a dual in-line ball mounter comprising two parallel ball mount cells. The two ball mount cells of the dual in-line ball mounter feed devices to a single reflow oven and a single flux cleaner to form a more efficient BGA ball mount line.
In one embodiment, the present invention is a BGA ball mount line, comprising (a) first and second loading cells; (b) a dual in-line ball mounter comprising first and second ball mount cells, wherein the first loading cell is configured to transfer a first stream of BGA devices to the first ball mount cell; the second loading cell is configured to transfer a second stream of BGA devices to the second ball mount cell; and the first and second ball mount cells are configured to operate concurrently to mount solder balls onto the first and second streams of BGA devices; (c) a first transfer cell configured to receive the first and second streams of BGA devices from both the first and second ball mount cells of the dual in-line ball mounter; (d) a reflow oven configured to receive the first and second streams of BGA devices from the first transfer cell and perform a single reflow process concurrently on both the first and second streams of BGA devices; (e) a flux cleaner configured to receive the first and second streams of BGA devices from the reflow oven and clean flux concurrently from both the first and second streams of BGA devices; (f) a second transfer cell configured to receive the first and second streams of BGA devices from the flux cleaner; and (g) first and second offloading cells, wherein the first offloading cell is configured to receive the first stream of BGA devices from the second transfer cell; and the second offloading cell is configured to receive the second stream of BGA devices from the second transfer cell.